Equipment for detecting improper wiring in portable installation

ABSTRACT

A power wiring error indicator for electrical equipment includes an indicator means coupled between equipment ground and the neutral terminal of a three-phase, four-wire system, or a single phase, three-wire system. Capacitors are connected between each line terminal and equipment ground to provide a return circuit for the indicator means.

United States Patent [151 3,696,291 Home [451 Oct, 3, 1972 EQUIPMENT FORDETECTING 3,382,410 /1968 Grimm ..'...3l7/l8 IMPROPER WIRING IN PORTABLEINSTALLATION FOREIGN PATENTS OR APPLICATIONS [72] Inventor: Arthur P.Home, Portland, Oreg. g rea 11 am [73] Assignee: ElectronicsDiversified, Inc., Portland, Oreg. OTHER PUBLICATIONS [22] Filed: Jan.30, 1970 Loewe, R. Check that Ground, Allis Chalmers Electripp NO 7 009cal Review Second Quarter 1948 FIGS. l- 5 Primary ExaminerGerard H.Strecker [52] US. Cl ..324/51, 324/66 Att rn y u h Blore, Klarquist &sparkman [51] Int. Cl. ..G0lr 31/02 [58] Field of Search ..324/51, 54,107, 108, 133; [57] ABSTRACT 340/255; 317/18 A power wiring errorindicator for electrical equip- [56] R f Ct d ment includes an indicatormeans coupled between e erences I e equipment ground and the neutralterminal of a three- UNITED STATES PATENTS phase, four-wire system, or asingle phase, three-wire system. Capacitors are connected between eachline g fi t terminal and equipment ground to provide a return Mrs 011...th t 1,744,840 1/1930 Strieby et a1 ..324/133 x or e or means 3,356,93912/ I967 Stevenson ..324/51 7 Claims, 3 Drawing Figures 76 L3 A f 36 A4656 66 em L2 A e5 e-E-c- L I k m! I q a 24 29] 44 54 64 v ce l Llv e l kI 32 23 P A 4| 5| 6! G C- 5) BACKGROUND OF THE INVENTION Frequentelectrical connection must be made to portable or semi-portableelectrical equipment such as mobile machinery, heavy duty electronicequipment, load control systems, or the like. These equipments oftenemploy three and four-wire input circuits where there is a danger inmaking the connection improperly, with resultant damage to theequipment. In the case of a portable light dimmer system for theatricalpresentations, a comparatively heavy lighting load is usually involvedand hence a single phase three-wire, or a three phase, four-wire powersource will be the usual input to the dimmer apparatus. Several lightingcircuits are then energized between plural conductors and a commonneutral. It is often difficult to ascertain the proper connection of thedimmer system to the power means in an unfamiliar building and theconnection may be improperly made.

SUMMARY OF THE INVENTION According to the present invention a powerwiring indicator provides a warning that the input power connection hasbeen improperly made, or alternatively, may warn of equipment failuresuch as a short circuit or the like. Indicator means, preferablycomprising a neon lamp, is connected between a neutral input terminal ofan electrical equipment and the equipment ground. Also, capacitors arepreferably interposed between each line terminal and the equipment orchassis ground. The equipment itself is ordinarily turned off as byopening circuit breakers provided therefor until the input power wiringis completed. Of course, the power circuit to which connection is madeis also preferably deenergized by removing building fuses, opening maincircuit breakers, or the like. After the connection is made, power issupplied from the building to the input terminals of the equipment. Ifwires have been interchanged, an indication of the improper connectionis given.

The equipment is preferably provided with a separate chassis orequipment ground. However, assuming that a nearby building ground is notavailable and none is used, it is possible due to equipment failure thatthe equipment chassis can reside at some high potential during operationof the equipment, thus endangering operating personnel. However, thepresent circuit also provides an indication of an improper voltage onthe equipment chassis after full energization thereof.

It is accordingly an object of the present invention to provide animproved power wiring error indicator for giving warning of improperwiring input connection from a single-phase, three-wire, or athree-phase, fourwire power source.

It is a further object of the present invention to provide an improvedpower wiring error indicator for giving warning in the case of undesiredreversal of equip ment power input leads.

It is a further object of the present invention to also provide anindicator for rendering warning in the case of a high potential presenton an accessible equipment chassis.

The subject matter which I regard as my invention is particularlypointed out and distinctly claimed in the concluding portion of thisspecification. The invention, however, both as to organization andmethod of operation, together with further advantages and objectsthereof,'may best beunderstood by reference to the following descriptiontaken in connection with the accompanying drawings wherein likereference characters refer to like elements.

DRAWINGS FIG. 1 is a front view of a wiring panel for electricalequipment, incorporating a power wiring error indicator according to thepresent invention;

FIG. 2 is a schematic diagram of the FIG. 1 panel and equipmentempowered therefrom; and

FIG. 3 is another front view of the FIG. 1 panel, illustrating wiringfor a single phase three-wire system in place of a three-phase,four-wire system.

DETAILED DESCRIPTION Referring to FIG. Lillustrating an equipment wiringpanel incorporating the power wiring error indicator. according to thepresent invention, this wiring panel comprises a terminal block 10 ofinsulating material secured to the metal frame or chassis 12 of anelectrical equipment. In a specific example, this electrical equipmentcomprised a portable dimmer system for lighting circuitry, which will bedescribed hereinafter in greater detail. Terminal block 10 carries aplurality of parallel metal terminal bars, 21 through 25, separated bybarriers 16 located therebetween and forming part of terminal block 10.Conductors which are connected by the terminal bars are received withinrecessed ends of the terminal bars under tension screws 18. On theequipment side of the terminal bars, these conductors may extend throughinsulating grommets 20 and provide a source of power as hereinafter morefully described. As illustrated, one such wire 26 extends from the topof terminal bar 21, three wires 27 from terminal bar 22, and pairs ofwires, 28, 29, and 30, respectively, from terminal bars 23, 24, and 25.Terminal bar 21 is intended for connection at its lower end to ground,while terminal bar 22 is adapted to receive the neutral conductor markedN. Lines L1, L2, and L3 are the three lines of a three-phasedistribution system wherein the voltages on these lines with respect toneutral connection N are equal but degrees out of phase with oneanother. Lines L1, L2, and L3 are correctly connected to terminal bars23, 24, and 25, respectively, as shown.

The input power connection illustrated in FIG. 1 may be characterized asa three-phase, four-wire input. The ground connection marked GND atterminal 21 suitably comprises a nearby building ground such as a water'pipe or the like, separate from the remaining conductors. Terminal bar21 is then connected at its upper end via conductor 26 to the equipmentchassis.

The external building ground ordinarily prevents an undesired electricalpotential from appearing on the chassis with respect to ground, whichmight be injurious to operatingpersonnel.

According to the present invention, an indicator means, here comprisinga neon lamp 38 in series with a current limiting resistor 40, isconnected between terminal bars 21 and 22, e.g., between the chassisground and the terminal bar employed for connection to the neutralsupply line. Also, capacitors 32, 34, and 36 are respectively interposedbetween terminal bars 23, 24, and and the chassis ground. As willhereinafter more fully appear, neon lamp 38 will light under a number ofdifferent conditions of misconnection of the input power lines.

The capacitance values of capacitors 32, 34, and 36 are equal, being0.005 microfarads in the case of equipment of a specific embodiment.Resistor 40 of this specific embodiment had a value of 100 K ohms.Although capacitances 32,34,36 are preferred, other high impedance meansmay be substituted therefor in certain instances. Likewise otherindicator means may be substituted for the neon lamp, although the neonlamp is preferred for providing a good indication with minimum current.

Referring more particularly to FIG. 2, the circuit provided by terminalblock 10, the dimmer system within chassis 12, and a lighting circuitryload is illustrated..Terminal blocks 21 through 25 are represented byjunction terminals 21' through 25 in the FIG. 2 diagram. As hereinbeforeindicated, terminal 21 is connected to chassis ground. Terminal 23 isconnected to line L1 and supplies power for lighting circuits comprisingparalleled lamps 71 and paralleled lamps 72 via a pair of wires 28. Thecircuit breaker 41 in series with a control circuit 51 is disposedbetween the terminal 23 and conductor 61 of the circuit comprising lamps7 1. Similarly, a circuit breaker 42 in series with control circuit 52is interposed between terminal 23 and conductor 62 supplying lamps 72;

Also, terminal 24 empowers paralleled lamps 73 and paralleled lamps 74through wires 29. Breaker 43 and control circuit 53 are disposed inseries between a wire 29 and conductor 63 leading to lamps 73, whilebreaker 44 and control circuit 54 are in series between the remainingwire 29 and conductor 64 connected to lamps 74. Further, terminal 25energizes lighting loads comprising paralleled lamps 75 and paralleledlamps 76 by way of wires having breaker 45 and control circuit 55 inseries with the conductor 65 leading to the lamp 75 circuit, and withbreaker 46 and control circuit 56 in series with the conductor 66leading to the lamp 76 circuit. The respective paralleled circuitsincluding lamps 71, 72, 73, 74, 75, and 76 are returned to neutralterminal 22 via wires 27. While there are actually a total of sixneutral return leads from the six separate lighting circuits,respectively, only three wires 27 are illustrated in FIG. 1, It isappreciated that the returns may be commoned in pairs as illustrated inFIG. 2 such that only three wires or less need be brought out to theterminal block.

In the case of the individual dimmer circuits within chassis 12, acontrol circuit such as control circuit 51 suitably acts to adjustablyreduce the power delivered to paralleled lamps 71. One such advantageoussystem control circuit 51 includes a pair of reversely connected siliconcontrolled rectifiers in series with the line and operative on eachalternating current cycle in selected phase relation. Thus, during eachhalf cycle of alternating current, the control circuit 51 is energizedat a selected time after the beginning of such half cycle for providingcurrent to paralleled lamps 71. This adjustment is achieved withoutsubstantial dissipation or waste of power when the lamps are to bedimmed. A circuit of this kind is more fully described in my copendingapplication Ser. No. 7093, filed Jan. 30,.

1970 entitled Control System," assigned to the assignee of the presentinvention. Since separate control circuits 51 through 56are employed forthe separate lighting circuits comprising lamps 71 through '76,respectively, individual control may be achieved in the six lightingcircuits.

FIG. 3 illustrates a variation in the wiring for the FIG. 1 paneladapting the apparatus for three-wire, single phase input. Theconnection is substantially similar to that illustrated in FIG. 1,except that lines L1 and L2 represent either side of the line withrespect to the neutral which is again connected to terminal bar 22.Terminal bar 25 is left unconnected. Wires 28 remain connected toterminal bar 23. However, wires 30' corresponding to wires 30 in FIGS. 1and 2, are inserted at the top of terminal bar 24, while one of wires29', corresponding to wires 29 in FIGS. 1 and 2, is connected toterminal bar 23 with the other being connected to terminal bar 24. Theneutral wires 27 remain in connection with terminal vbar 22. Thus, thesix lighting circuits are here divided between the two lines, with threelighting circuits being empowered from one line while the threeremaining lighting circuits are empowered from the other. The errorindicator operation will remain substantially the same as hereinaftermore fully indicated.

Since the light vdimmer system is a semi-portable apparatus, frequentconnection to power service is required by personnel. often not havingextensive electrical knowledge. The identity of each conductor may notalways be clear even to those skilled in the art when conductors arebrought in from a remote location, unless the lines are first energizedfor conducting a test.

According to the present invention, the connection of the two or threelines and neutral is made to the equipment preferably with the linesdeenergized, and indication will subsequently be given if the connectionhas been made improperly. The lines L1, L2, and L3 (in the case of threephase power) are first deenergized, for example, by removing the mainbuilding fuses or operating the main circuit breakers to disconnectposition. Also at this time, the present equipment is deenergized as byoperating disconnect switching in each of the control circuits 51 to 56and/or by opening each of the circuit breakers 41 to 46. A buildingground is desirably also connected to the apparatus as hereinbeforeindicated for securely grounding the chassis of the equipment andprotecting the users thereof. The neutral line is also ordinarilygrounded at the input power distribution point of the building, but thisdoes not imply that the chassis ground terminal bar 21 should beconnected to the supposed neutral line. Terminal bar 21 is desirablyconnected to a local building ground point or left disconnected.

After connection to the terminal block, power is applied to the inputlines by restoring the building fuse or breaker connection. If theconnections have been properly made, and if a local building ground isprovided, neon lamp 38 will fail to light inasmuch as neutral terminalbar 22 will be at the same potential as ground terminal bar 21. Even ifno ground has been provided to the ground terminal bar 21, a phantomground is still provided by means of capacitors 32, 34, and 36, placingthe chassis at the neutral point with respect to power provided on linesL1, L2, and L3. Since the capacitors are of equal value, and since theline voltages are conventionally equal and mutually out of phase,thecapacitors provide a Y connection with zero voltage at their commonpoint.

If, however, the input lines have been miswired so that the neutral linehas been connected to terminal bar 23, 24, or 25, while one of the linesL1, L2, or L3 has been improperly connected to neutral terminal bar 22,

a difference in voltage will appear between terminal bar 22 and terminalbar 21 grounded to the chassis. If the local building ground has beenbrought in at terminal bar 21, and terminalbar 22 has been thusimproperly connected to the line having a voltage above neutral, it isapparent a voltage difference will appear across neon lamp 38 causingthe same to light. Even if a local building ground has not beenconnected to terminal bar 21, one or more of the capacitors 32, 34, and36 will provide a return for current to neon lamp 38. For example, oneof the terminal bars 23, 24, or 25 which has been improperly connectedto a neutral line will provide a return path in such case so thatindication of improper wiring will still be given. It should be apparentthat operation will be the same in the case of either a three-phase,four-wire connection or in the case of a single phase, three-wireconnection. The capacitors 32, 34 and/or 36 see only the neon lampcurrent which is quite small and these capacitors need be only of smallcapacitance value in order to carry that current.

If neon lamp 38 does not light with the input lines connected, the loadsare energized via the switching in control circuits 51-56, and/orbreakers 41 through 46 are closed. If the lamp 38 now lights, it mayindicate the miswiring of the lines L1, L2, and/or L3 in the absence ofa neutral connection to terminal bar 22 but assuming a local ground wirehas been connected to terminal bar 21. If the neutral line has beenimproperly connected at terminal bar 23, 24, or 25, the voltage atterminal bar 22 will be offset with respect to ground through the lamploads. Therefore, a voltage will then appear at nonconnected neutralterminal bar 22 and lamp 38 will light. The lamp loads in that instanceestablish a voltage other than zero at terminal bar 22 even though theloads are balanced. If the loads are unbalanced and terminal bar 22 hasnot been connected, lamp 38 will light in any case indicating the loadsshould be balanced or a neutral connected.

Also, if a connection has been improperly made, or the equipment isfaulty such that the chassis is hot or resides at some voltage withrespect to ground (assuming no ground connection has been made toterminal bar 21), lamp 38 will light inasmuch as there is a voltage atthe grounded chassis with respect to the neutral connection. Let usassume a short circuit in the system, e.g., that a wire has becomeimproperly connected to the equipment chassis. The voltage on thechassis will light neon lamp 38 if terminal bar 22 is properly connectedto a neutral line, or even in the absence of such neutral line atterminal bar 22, if the neutral line is not also miswired to the voltageas now appears on the chassis. Thus, ordinarily in the absence of aconnection of the neutral line at terminal bar 22, if the chassisresides at a high voltage, the phantom" neutral is provided through theload circuits with this neutral providing a different voltage level atterminal bar 22 from the voltage which now appears on the chassis,causing the lamp 38 to light. If a high voltage line is improperlyconnected to ground terminal bar 21 placing high voltage on the chassis,the circuit operates in a substantially similar manner detecting voltageon the chassis different from the voltage level at neutral terminal bar22.

Thus, the wiring indicator according to the present invention detects avariety of miswiring conditions or faulty equipment connection oroperation, before the equipment is damaged by these circumstances, orbefore injury occurs to operating personnel. The circuit is simple, buteffects an increase in the speed with which the equipment can beconnected to power mains with reasonable assurance that such connectionwill have been properly made.

While I have shown and described preferred embodiments of my invention,it will be apparent to those skilled in the art that many changes andmodifications may be made without departing from my invention in itsbroader aspects. I therefore intend the appended claims to cover allsuch changes and modifications as fall within the true spirit and scopeof my invention.

What is claimed is:

1. An electrical equipment comprising:

plural terminal means for receiving electrical conductors for empoweringsaid electrical equipment, said terminal means including a neutralterminal adapted for connection to a neutral line, and at least two lineterminals wherein said two line terminals are adapted to receive linesproviding separate voltages with respect to said neutral line forempowering said equipment,

said equipment further including a circuit reference terminal adapted toreceive an external ground connection separate from said electricalconductors for empowering said equipment, but selectively ungrounded,

indicator means coupled between said neutral terminal and said referenceterminal and responsive to a difference in voltage therebetween fordelivering an indication upon improper, energization of said terminals,

and separate relatively high impedance means of substantially equalimpedance coupled between each of said line terminals and said referenceterminal for completing a circuit for establishing a phantom groundreturn for said means for delivering an indication in the absence of anexternal ground connection to said circuit reference terminal.

2. The equipment according to claim 1 wherein said means for deliveringan indication comprises a neon lamp and a resistance in series therewithconnected between said neutral terminal and said reference terminal.

3. The equipment according to claim 1 further including means on theload side of said terminal means for disconnecting said equipment.

4. The equipment according to claim 3 further including separate loadcircuits connected to said line terminals via the disconnecting means,said load circuits being returned in common to said neutral terminal.

5. The equipment according to claim 4 including three line terminalseach adapted to be energized by a line providing a separate voltage withrespect to neutral in a three phase system, and six load circuits forconnection in pairs to said three line terminals by way of saiddisconnecting means, and means for alternatively connecting said loadcircuits in groups of three to each of a pair of said line terminalswhen only line terminals of said pair are energized with respect toneutral from a single phase, three-wire system.

6. An electrical equipment comprising:

plural terminal means for receiving electrical conductors for empoweringsaid electrical equipment, said terminal means including a neutralterminal adapted for connection to a neutral line and at least two lineterminals wherein said two line terminals are adapted to receive linesproviding separate voltages with respect to said neutral line forempowering said equipment,

said equipment further including a circuit reference terminal adapted toreceive an external ground connection separate from said electricalconductors for empowering said equipment,

indicator means coupled between said neutral terminal and said referenceterminal and responsive to a difference in voltage therebetween fordelivering an indication upon improper energization of said terminals,

and separate capacitor means of substantially equal impedance coupledbetween each of said line terminals and said reference terminal forcompleting a circuit for establishing a phantom ground return for saidmeans for delivering an indication in the absence of an external groundconnection to said circuit reference terminal.

7. An electrical equipment comprising:

plural terminal means for receiving electrical conductors for empoweringsaid electrical equipment,

saidterminal means including a neutral terminal adapted for connectionto a neutral line, and at ing an indication upon improper energizationof said terminals,

and separate relatively high impedance capacitor means of substantiallyequal impedance coupled between each of said line terminals and saidreference terminal for completing a circuit for establishing a phantomground return for said meansfor delivering an indication in the absenceof an external ground connection to said circuit reference terminal.

1. An electrical equipment comprising: plural terminal means forreceiving electrical conductors for empowering said electricalequipment, said terminal means including a neutral terminal adapted forconnection to a neutral line, and at least two line terminals whereinsaid two line terminals are adapted to receive lines providing separatevoltages with respect to said neutral line for empowering saidequipment, said equipment further including a circuit reference terminaladapted to receive an external ground connection separate from saidelectrical conductors for empowering said equipment, but selectivelyungrounded, indicator means coupled between said neutral terminal andsaid reference terminal and responsive to a difference in voltagetherebetween for delivering an indication upon improper energization ofsaid terminaLs, and separate relatively high impedance means ofsubstantially equal impedance coupled between each of said lineterminals and said reference terminal for completing a circuit forestablishing a phantom ground return for said means for delivering anindication in the absence of an external ground connection to saidcircuit reference terminal.
 2. The equipment according to claim 1wherein said means for delivering an indication comprises a neon lampand a resistance in series therewith connected between said neutralterminal and said reference terminal.
 3. The equipment according toclaim 1 further including means on the load side of said terminal meansfor disconnecting said equipment.
 4. The equipment according to claim 3further including separate load circuits connected to said lineterminals via the disconnecting means, said load circuits being returnedin common to said neutral terminal.
 5. The equipment according to claim4 including three line terminals each adapted to be energized by a lineproviding a separate voltage with respect to neutral in a three phasesystem, and six load circuits for connection in pairs to said three lineterminals by way of said disconnecting means, and means foralternatively connecting said load circuits in groups of three to eachof a pair of said line terminals when only line terminals of said pairare energized with respect to neutral from a single phase, three-wiresystem.
 6. An electrical equipment comprising: plural terminal means forreceiving electrical conductors for empowering said electricalequipment, said terminal means including a neutral terminal adapted forconnection to a neutral line and at least two line terminals whereinsaid two line terminals are adapted to receive lines providing separatevoltages with respect to said neutral line for empowering saidequipment, said equipment further including a circuit reference terminaladapted to receive an external ground connection separate from saidelectrical conductors for empowering said equipment, indicator meanscoupled between said neutral terminal and said reference terminal andresponsive to a difference in voltage therebetween for delivering anindication upon improper energization of said terminals, and separatecapacitor means of substantially equal impedance coupled between each ofsaid line terminals and said reference terminal for completing a circuitfor establishing a phantom ground return for said means for deliveringan indication in the absence of an external ground connection to saidcircuit reference terminal.
 7. An electrical equipment comprising:plural terminal means for receiving electrical conductors for empoweringsaid electrical equipment, said terminal means including a neutralterminal adapted for connection to a neutral line, and at least two lineterminals wherein said two line terminals are adapted to receive linesproviding separate voltages with respect to said neutral line forempowering said equipment, said equipment further including a circuitreference terminal adapted to receive an external ground connectionseparate from said electrical conductors for empowering said equipment,indicator means coupled between said neutral terminal and said referenceterminal and responsive to a difference in voltage therebetween fordelivering an indication upon improper energization of said terminals,and separate relatively high impedance capacitor means of substantiallyequal impedance coupled between each of said line terminals and saidreference terminal for completing a circuit for establishing a phantomground return for said means for delivering an indication in the absenceof an external ground connection to said circuit reference terminal.